|Group||6||Melting point||2622 oC, 4752 oF, 2895 K|
|Period||5||Boiling point||4639 oC, 8382 oF, 4912 K|
|Block||d||Density (g cm-3)||10.2|
|Atomic number||42||Relative atomic mass||95.95|
|State at 20°C||Solid||Key isotopes||95Mo, 96Mo, 98Mo|
|Electron configuration||[Kr] 4d55s1||CAS number||7439-98-7|
|ChemSpider ID||22374||ChemSpider is a free chemical structure database|
Most molybdenum is used to make alloys. It is used in steel alloys to increase strength, hardness, electrical conductivity and resistance to corrosion and wear. These ‘moly steel’ alloys are used in parts of engines. Other alloys are used in heating elements, drills and saw blades.
Molybdenum disulfide is used as a lubricant additive. Other uses for molybdenum include catalysts for the petroleum industry, inks for circuit boards, pigments and electrodes.
There are about 50 different enzymes used by plants and animals that contain molybdenum. One of these is nitrogenase, found in nitrogen-fixing bacteria that make nitrogen from the air available to plants. Leguminous plants have root nodules that contain these nitrogen-fixing bacteria.
|Common oxidation states||6, 5, 4, 3, 2, 0|
|Isotopes||Isotope||Atomic mass||Natural abundance (%)||Half life||Mode of decay|
|92Mo||91.907||14.77||> 3 x 1017 y||β+-EC|
|100Mo||99.907||9.67||6 x 1020 y||β-β-|
Specific heat capacity
(J kg-1 K-1)
|251||Young's modulus (GPa)||Unknown|
|Shear modulus (GPa)||Unknown||Bulk modulus (GPa)||231|
The soft black mineral molybdenite (molybdenum sulfide, MoS2), looks very like graphite and was assumed to be a lead ore until 1778 when Carl Scheele analysed it and showed it was neither lead nor graphite, although he didn’t identify it.
Others speculated that it contained a new element but it proved difficult to reduce it to a metal. It could be converted to an oxide which, when added to water, formed an acid we now know as molybdic acid, H2MoO4, but the metal itself remained elusive.
Scheele passed the problem over to Peter Jacob Hjelm. He ground molybdic acid and carbon together in linseed oil to form a paste, heated this to red heat in and produced molybdenum metal. The new element was announced in the autumn of 1781.
|Listen to Molybdenum Podcast|
Chemistry in its element - molybdenum
You're listening to Chemistry in its Element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry
This week, we clarify the importance of the often misunderstood molybdenum. Here's Quentin Cooper:
The answer to the ultimate question - of life, the Universe and Everything - is, as every Douglas Adams fan knows, 42. And 42, as every Mendeleev fan knows, is the atomic number of molybdenum. And for many that - plus the indisputable fact that molybdenum is a funny word - is often about as far as their knowledge goes of this silvery metal - not that they'd have known it was a silvery metal - which is wedged between its better known brethren chromium and tungsten in group six of the periodic table. That odd-sounding name comes in a convoluted way from the Greek for lead, as ores of the two were often mixed up by early mineralogists - it was also frequently mistaken for graphite - and it wasn't until 1778 that molybdenum was recognised as a distinct entity deserving its own place in the periodic table, and a few years later still that it was finally isolated. The key breakthrough came from the Swedish chemist Carl Wilhlelm Scheele, better known as 'Hard luck Scheele' because he made a whole series of chemical discoveries, including oxygen, only for others to go and get the credit.
So its mistaken-identity history, its miscredited discoverer, its misleading and often mis-spelled name, all add to the aura of comedy and confusion around molybdenum.....and yet it's an element that's right at the root of life - not just human life, but pretty much all life on the planet: yes you'll find tiny amounts of it in everything from the filaments of electric heaters to missiles to protective coatings in boilers, and its high performance at high temperatures mean it has a range of commercial applications: it's useful in toughening up steel and giving it more corrosion resistance, as a catalyst in processes such as refining petroleum, and above all it's turned to when you need things to get hot but stay slippy - where WD40 and other petroleum derived oils are at risk of igniting, molybdenum sulfides are the basis of a range of lubricants which can cope with the heat and keep things moving smoothly.
But for all the ways we've discovered to use it, of far greater significance - although involving far smaller quantities of molybdenum - is the way we've evolved to make use of it within us. It's found in dozens of enzymes... including all important nitrogenase, which allows the most abundant element in the atmosphere, nitrogen, to be taken up and turned into compounds that enable bacteria, plants, us and everything between to synthesise and utilise proteins. Without proteins there wouldn't be much at all in the way of life....and without molybdenum there wouldn't be much at all in the way of proteins. And it turns up in other key human enzymes too such as xanthine oxidase in the liver, which is vital to our waste processing.
But just in case anyone's thinking of rushing off to buy one of the many commercially available trace mineral supplements with molybdenum it's worth adding that although like much of life on Earth we definitely need it.... we don't need that much of it: about a third of a gram is all you'll get through in an entire lifetime. That's next to nothing...but without it we'd be next to nothingness.
So, time to stop laughing at the funny name... molybdenum really is one of life's few true essentials.
So time to give some much-owed respect, it seems, to the element molybdenum. That was science broadcaster Quentin Cooper with the widely applied chemistry of molybdenum. Now, next week, blink and you may miss it.
If elements were insects, darmstadtium would be the mayfly of the chemical world. It exists for the most fleeting time before it transforms to something else. Darmstadium is never going to have a practical use - but its sheer brevity of existence gives it a wistful fascination.
And to find out what does happen in darmstadtium's brief existence on earth, in next week's Chemistry in its element. Until then, I'm Meera Senthilingham and thank you for listening.
Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements.
Mining and Sourcing data: British Geological Survey – natural environment research council.
Text: John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.